FILE PHOTO: Germany's Minister of State for Europe Michael Roth listens to a journalist ask a question about Britain's Foreign Secretary Boris Johnson, during his press conference with British Minister of State for Europe and the Americas Alan Duncan and Polish Minister of Foreign Affairs Jacek Czaputowicz at the Western Balkans Summit in London, Britain, July 9, 2018. Matt Dunham/Pool via REUTERS

BERLIN (Reuters) - Peace in Northern Ireland and the integrity of the EU single market are non-negotiable for the EU, Germany’s Minister for European Affairs Michael Roth said hours before British Prime Minister Boris Johnson will meet Chancellor Angela Merkel in Berlin.

“Spinning gold from straw has never yet worked. That is also true of Brexit. Peace in Northern Ireland as well as the integrity of the internal market are not negotiable for the EU,” Roth tweeted on Wednesday.